Semiconductor device including epitaxial region

ABSTRACT

A semiconductor device is provided. The semiconductor device includes: an active region on a semiconductor substrate; a channel region on the active region; a source/drain region adjacent to the channel region on the active region; a gate structure overlapping the channel region, on the channel region; a contact structure on the source/drain region; a gate spacer between the contact structure and the gate structure; and a contact spacer surrounding a side surface of the contact structure. The source/drain region includes a first epitaxial region having a recessed surface and a second epitaxial region on the recessed surface of the first epitaxial region, and the second epitaxial region includes an extended portion, extended from a portion overlapping the contact structure in a vertical direction, in a horizontal direction and overlapping the contact spacer in the vertical direction.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims benefit of priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2019-0148399, filed on Nov. 19, 2019, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND 1. Field

The present inventive concept relates to a semiconductor device, and particularly, to a semiconductor device including an epitaxial region and a formation method thereof.

2. Description of Related Art

As demand for high performance, high speed, and/or multi-functionalization of a semiconductor device increases, a degree of integration of such a semiconductor device is increasing. Due to the trend for higher integration of semiconductor devices, a size of a planar metal-oxide-semiconductor field-effect transistor (MOSFET) has been reduced. In order to overcome the limitations of the operating characteristics caused by the reduction in a size of the MOSFET, efforts are being made to develop a MOSFET including a channel having a three-dimensional structure.

SUMMARY

An aspect of the present inventive concept is to provide a semiconductor device capable of improving a degree of integration.

An aspect of the present inventive concept is to provide a semiconductor device having improved performance.

An aspect of the present inventive concept is to provide a method of forming a semiconductor device having improved productivity of a semiconductor device.

According to an aspect of the present inventive concept, a semiconductor device is provided. A semiconductor device includes: an isolation layer defining a first active region on a semiconductor substrate; an interlayer insulating layer on the isolation layer; a channel region on the first active region; a source/drain region adjacent to the channel region in a first horizontal direction on the first active region; a gate structure overlapping the channel region and extending lengthwise in a second horizontal direction perpendicular to the first horizontal direction, on the channel region; a contact structure on the source/drain region; a gate spacer between the contact structure and the gate structure; and a contact spacer disposed between the contact structure and the gate spacer and disposed between the contact structure and the interlayer insulating layer. A lower end of the contact spacer and a lower end of the gate spacer are disposed at different height levels, the contact structure includes a metal-semiconductor compound layer, and a contact plug on the metal-semiconductor compound layer, the source/drain region includes a first epitaxial region having a recessed surface and a second epitaxial region on the recessed surface of the first epitaxial region, an upper surface of the second epitaxial region is in contact with the metal-semiconductor compound layer, and the second epitaxial region includes an extended portion, extending lengthwise in the first horizontal direction from a portion overlapping the contact structure in a vertical direction to a portion overlapping the contact spacer in the vertical direction.

According to an aspect of the present inventive concept, a semiconductor device is provided. The semiconductor device includes: an active region on a semiconductor substrate; a channel region on the active region; a source/drain region adjacent to the channel region on the active region; a gate structure overlapping the channel region, on the channel region; a contact structure on the source/drain region; a gate spacer between the contact structure and the gate structure; and a contact spacer surrounding a side surface of the contact structure. The contact structure includes a metal-semiconductor compound layer, and a contact plug on the metal-semiconductor compound layer, the source/drain region includes a base epitaxial region, a first epitaxial region on the base epitaxial region and a second epitaxial region on the first epitaxial region, the source/drain region includes a Si element and a Ge element, a Ge element concentration in the base epitaxial region, a Ge element concentration in the first epitaxial region, and a Ge element concentration in the second epitaxial region are different from each other, an upper surface of the second epitaxial region is in contact with the metal-semiconductor compound layer, and the second epitaxial region includes an extended portion, extending in a horizontal direction from a portion overlapping the contact structure in a vertical direction to a portion overlapping the contact spacer in the vertical direction.

According to an aspect of the present inventive concept, a semiconductor device is provided. The semiconductor device includes: an active region on a semiconductor substrate; a channel region on the active region; a source/drain region adjacent to the channel region on the active region; a gate structure overlapping the channel region, on the channel region; a contact structure on the source/drain region; a gate spacer between the contact structure and the gate structure; and a contact spacer surrounding a side surface of the contact structure. A lower end of the contact spacer and a lower end of the gate spacer are disposed at different height levels, the source/drain region includes a first epitaxial region having a recessed surface and a second epitaxial region on the recessed surface of the first epitaxial region, and the second epitaxial region includes an extended portion, extending in a horizontal direction from a portion overlapping the contact structure in a vertical direction to a portion overlapping the contact spacer in the vertical direction.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a plan view illustrating a semiconductor device, according to example embodiments;

FIGS. 2A to 2C are partially enlarged cross-sectional views illustrating a semiconductor device, according to example embodiments of the present disclosure;

FIGS. 3A to 3D are partially enlarged cross-sectional views illustrating various modified examples of a semiconductor device, according to example embodiments of the present disclosure;

FIGS. 4A to 4C are partially enlarged cross-sectional views illustrating various modified examples of a semiconductor device, according to example embodiments of the present disclosure;

FIG. 5 is a cross-sectional view illustrating a modified example of a semiconductor device, according to example embodiments of the present disclosure;

FIG. 6 is a cross-sectional view illustrating a modified example of a semiconductor device, according to example embodiments of the present disclosure;

FIG. 7 is a plan view illustrating a modified example of a semiconductor device, according to example embodiments of the present disclosure;

FIG. 8 is a cross-sectional view illustrating a modified example of a semiconductor device, according to example embodiments of the present disclosure;

FIGS. 9A to 9D are cross-sectional views illustrating various modified examples of a semiconductor device, according to example embodiments of the present disclosure;

FIG. 10 is a plan view illustrating a modified example of a semiconductor device, according to example embodiments of the present disclosure;

FIGS. 11A to 11C are diagrams illustrating a modified example of a semiconductor device, according to example embodiments of the present disclosure;

FIGS. 12A to 12C are cross-sectional views illustrating various modified examples of a semiconductor device, according to example embodiments of the present disclosure;

FIG. 13 is a cross-sectional view illustrating a modified example of a semiconductor device, according to example embodiments of the present disclosure;

FIG. 14 is a cross-sectional view illustrating a modified example of a semiconductor device, according to example embodiments of the present disclosure;

FIG. 15 is a process flow diagram illustrating a method of manufacturing a semiconductor device, according to example embodiments of the present disclosure;

FIGS. 16A to 16B are cross-sectional views illustrating a method of manufacturing a semiconductor device, according to example embodiments of the present disclosure;

FIGS. 17A to 17B are cross-sectional views illustrating a method of manufacturing a semiconductor device, according to example embodiments of the present disclosure; and

FIGS. 18A to 18B are cross-sectional views illustrating a method of manufacturing a semiconductor device, according to example embodiments of the present disclosure.

DETAILED DESCRIPTION

First, referring to FIGS. 1, 2A, and 3B, a semiconductor device according to an example embodiment of the present disclosure will be described. FIG. 1 is a plan view illustrating a semiconductor device according to example embodiments of the present to disclosure, FIG, 2A is a cross-sectional view illustrating a region taken along line and a region taken along line IIa-IIa′ of FIG. 1, to describe a semiconductor device according to example embodiments of the present disclosure, FIG. 2B is a partially enlarged view enlarging a portion indicated by ‘A’ of FIG. 2A, and FIG. 2C is a cross-sectional view illustrating a region taken along line IIIa-IIIa′ of FIG. 1 to describe a semiconductor device according to example embodiments of the present disclosure.

Referring to FIGS. 1, and 2A to 2C, a semiconductor device 1 according to example embodiments includes a semiconductor substrate 3, an active region 6 and an isolation layer 9 on the semiconductor substrate 3, and a channel region 6 p and a source/drain region 21 a on the active region 6. The semiconductor substrate 3 may be formed of a semiconductor material such as silicon.

In an example, the active region 6 may have a linear shape or a bar shape extending lengthwise in a first horizontal direction D1. The first horizontal direction D1 may be parallel to an upper surface of the semiconductor substrate 3.

In an example, the isolation layer 9 may be a trench isolation layer (e.g., a shallow trench isolation layer). The isolation layer 9 may be formed of an insulating material such as silicon oxide, or the like.

In an example, the channel region 6 p may be extended from the active region 6 in a vertical direction D3. For example, the channel region 6 p may be formed at a vertical level higher than an upper surface of the isolation layer 9. The channel region 6 p may be referred to as an active fin.

In an example, when the channel region 6 p is a channel region of a PMOS transistor, the channel region 6 p may have an N-type conductivity, and the source/drain region 21 a may have a P-type conductivity. As another example, when the channel region 6 p is a channel region of an NMOS transistor, the channel region 6 p may have a P-type conductivity, and the source/drain region 21 a may have an N-type conductivity.

The semiconductor device 1 may further include a gate structure 36 overlapping the channel region 6 p on the active region 6, extending lengthwise in a second horizontal direction D2 perpendicular to the first horizontal direction D1, and overlapping the isolation layer 9 in the vertical direction D3, and a gate spacer 15 on a side surface of the gate structure 36. The gate structure 36 may extend lengthwise in the second horizontal direction D2 while covering an upper surface and a side surface of the channel region 6 p.

The gate structure 36 may include a gate electrode 42, a gate dielectric layer 39 covering a lower surface and a side surface of the gate electrode 42, and a gate capping layer 45 on the gate electrode 42. The gate capping layer 45 may cover an upper end of the gate dielectric layer 39. In some embodiments, the gate dielectric layer 39 may contact the lower and side surfaces of the gate electrode 42. An upper surface of the gate dielectric layer 39 may be coplanar with an upper surface of the gate electrode 42. The gate capping layer 45 may contact the upper surfaces of the gate dielectric layer 39 and the gate electrode 42. Side surfaces of the gate dielectric layer 39 and the gate capping layer 45 may be aligned with one another in the vertical direction, and the gate spacer 15 may contact the side surfaces of the gate dielectric layer 39 and the gate capping layer 45. As used herein, the term “contact” refers to a direct connection touching) unless the context indicates otherwise.

The gate dielectric layer 39 may include silicon oxide and/or a high-k dielectric. The gate electrode 42 may be formed of a conductive material such as doped silicon, metal nitride (e.g., TiN, TaN, WN, or the like), a metal (e.g., W, or the like), or the like. The gate capping layer 45 may be formed of an insulating material such as SiN, SiON, or the like. The gate spacer 15 may be formed of an insulating material such as SiO, SiN, SiON, SiOC, or the like.

The source/drain region 21 a may be adjacent to the channel region 6 p in the first horizontal direction D1 on the active region 6. For example, each channel region 6 p may be provided between adjacent pairs of the source/drain regions 21 a.

On the source/drain region 21 a, a contact hole 48 may be disposed. The contact hole 48 may be defined by the interlayer insulating layer 30 in the second horizontal direction D2 and defined by the gate spacer 15 in the first horizontal direction D1.

The semiconductor device 1 may further include a contact structure 57 on the source/drain region 21 a. The contact structure 57 may include a metal-semiconductor compound layer 60 and a contact plug 63 on the metal-semiconductor compound layer 60. The contact structure 57 may be disposed in the contact hole 48. The metal-semiconductor compound layer 60 may be a metal-silicon alloy layer, a metal-germanium alloy layer, or a metal-silicon-germanium alloy layer. Here, a metal in the metal-semiconductor compound layer 60 may be titanium (Ti), tantalum (Ta), nickel (Ni), or cobalt (Co).

In an example, the metal-semiconductor compound layer 60 may have a thickness in the vertical direction D3 of about 1 nm to about 10 nm.

In an example, the contact plug 63 may include a first conductive layer 66 and a second conductive layer 69. The first conductive layer 66 may cover a lower surface and a side surface of the second conductive layer 69. The first conductive layer 66 may contact the lower and side surfaces of the second conductive layer 69, and a lower surface of the first conductive layer 66 may contact an upper surface of the metal-semiconductor compound layer 60. The first conductive layer 66 may include metal nitride such as TiN, TaN, WN, or the like, while the second conductive layer 69 may include a metal such as tungsten (W), or the like.

The semiconductor device 1 may further include a contact spacer 51 in the contact hole 48 and surrounding a side surface of the contact structure 57. The contact spacer 51 may be interposed between the contact structure 57 and the interlayer insulating layer 30 in the second horizontal direction D2 while being interposed between the contact structure 57 and the gate spacer 15 in the first horizontal direction D1. The contact spacer 51 may be formed of an insulating material such as silicon oxide. An outside surface of the contact spacer 51 may contact the interlayer insulating layer 30 and the gate spacer 15, and an inside surface of the contact spacer 51 may contact the contact structure 57.

In an example, a lower end of the contact spacer 51 may be disposed at a height (vertical) level lower than a lower end of the gate spacer 15. For example, the lower end of the contact spacer 51 may be disposed at a vertical level lower than an upper surface of the channel region 6 p.

In an example, a maximum thickness of the gate spacer 15 in the first horizontal direction D1 may be greater than a maximum thickness of the contact spacer 51 in the first horizontal direction D1.

The source/drain region 21 a may include a first epitaxial region 27 having a recessed surface 27 r and a second epitaxial region 54 on the recessed surface 27 r of the first epitaxial region 27. The first epitaxial region 27 may further include an upper end 27 t in contact with a lower surface of the gate spacer 15.

When a lower surface of the gate spacer 15 or an upper surface of the channel region 6 p is considered as a reference plane, a maximum depth of the recessed surface 27 r of the first epitaxial region 27 may be about 5 nm to about 50 nm. For example, the maximum depth of the recessed surface 27 r may be about 5 nm to about 50 nm below the reference plane defined by the lower surface of the gate spacer 15 or the upper surface of the channel region 6 p.

The source/drain region 21 a may further include a base epitaxial region 24. The base epitaxial region 24 may be disposed between the first epitaxial region 27 and the channel region 6 p and may be disposed between the first epitaxial region 27 and the active region 6. The base epitaxial region 24 may include an upper end 24 t coplanar with the upper end 27 t of the first epitaxial region 27.

In an example, the upper end 24 t of the base epitaxial region 24 and the upper end 271 of the first epitaxial region 27 may be in contact with a lower surface of the gate spacer 15.

An upper surface 54U of the second epitaxial region 54 may be in contact with the metal-semiconductor compound layer 60 of the contact structure 57.

In an example, the upper surface 54U of the second epitaxial region 54 may have a shape bent downwards. For example, the upper surface 54U of the second epitaxial region 54 may have a convex shape.

In an example, the upper surface 54U of the second epitaxial region 54 may be disposed at a height t than a lower surface of the gate spacer 15 and a lower surface of the gate structure 36. The upper surface 54U of the second epitaxial region 54 may be disposed at a height level lower than a lower surface of the contact spacer 51.

The second epitaxial region 54 may include an extended portion 54 p extended from a portion overlapping the contact structure 57 in the vertical direction D3, in the first horizontal direction D1 and overlapping the contact spacer 51 in the vertical direction D3. For example, a width in the first horizontal direction D1 of the second epitaxial region 54 including the extended portion 54 p may be greater than a width in the first horizontal direction D1 of the contact structure 57.

The extended portion 54 p of the second epitaxial region 54 may overlap the gate spacer 15 in the vertical direction D3. The extended portion 54 p of the second epitaxial region 54 may be spaced apart from the gate spacer 15. The second epitaxial region 54 may be in contact with a lower end 51L of the contact spacer 51.

The first epitaxial region 27 may include a first lower epitaxial region 27L positioned below the extended portion 54 p of the second epitaxial region 54 and a first upper epitaxial region 27U positioned above the extended portion 54 p of the second epitaxial region 54. For example, the first lower epitaxial region 27L may be the portion of the first epitaxial region 27 that is formed at a vertical level lower than the extended portion 54 p, and the first upper epitaxial region 27U may be the portion of the first epitaxial region 27 that is formed at a vertical level the same as or higher than the extended portion 54 p. The first lower epitaxial region 27L and the first upper epitaxial region 27U may be connected to each other. For example, the first lower epitaxial region 27L and the first upper epitaxial region 27U may be in material continuity with one another. As used herein, the term “material continuity” may refer to structures, patterns, and/or layers that are formed at the same time and of the same material, without a break in the continuity of the material of which they are formed.

A maximum width of the second epitaxial region 54 in the first horizontal direction D1 may be greater than a maximum width of the metal-semiconductor compound layer 60 in the first horizontal direction D1. A maximum width of the second epitaxial region 54 in the second horizontal direction D2 may be greater than a maximum width of the metal-semiconductor compound layer 60 in the second horizontal direction D2.

A transistor including the channel region 6 p, the source/drain region 21 a, and the gate structure 36 may be a PMOS transistor. The source/drain region 21 a may include a Si element and a Ge element. A Ge element concentration in the first epitaxial region 27 may be higher than a Ge element concentration in the base epitaxial region 24. A Ge element concentration in the second epitaxial region 54 may be higher than a Ge element concentration in the first epitaxial region 27.

In an example, the Ge element concentration in the base epitaxial region 24 may be about 1% to about 40%.

In an example, the Ge element concentration in the first epitaxial region 27 may be about 30% to about 90%.

The Ge element concentration in the second epitaxial region 54 may be about 50% to about 100%. The second epitaxial region 54 having a higher concentration of a Ge element, as compared with the base epitaxial region 24 and the first epitaxial region 27, may be a stressor applying compressive stress to the channel region 6 p. Thus, since charge mobility in the channel region 6 p could be increased, performance of a PMOS transistor including the channel region 6 p, the source/drain region 21 a, and the gate structure 36 may be improved.

The base epitaxial region 24 may have a thickness in the vertical direction D3 of about 1 nm to about 40 nm.

The first epitaxial region 27 may have a thickness in the vertical direction D3 of about 1 nm to about 50 nm

The second epitaxial region 54 may have a thickness in the vertical direction D3 of about 1 nm to about 50 nm.

The source/drain region 21 a. may include at least one among boron (B), aluminum (Al), gallium (Ga), and indium (In) as P-type impurities. A concentration of the P-type impurities of the source/drain region 21 a may be about 1E17 to about 1E22 atom/cc.

A maximum concentration of the P-type impurities in the second epitaxial region 54 may be higher than a minimum concentration of the P-type impurities in the first epitaxial region 27. The maximum concentration of the P-type impurities in the first epitaxial region 27 may be higher than a minimum concentration of the P-type impurities in the base epitaxial region 24.

The second epitaxial region 54 may be spaced apart from the channel region 6 p, and to may be in contact with the contact structure 57. For example, the base epitaxial region 24 and the first epitaxial region 27 may be between the second epitaxial region 54 and the channel region 6 p, separating the second epitaxial region 54 from the channel region 6 p. An impurity concentration of the second epitaxial region 54 in the source/drain region 21 a is highest among the base epitaxial region 24, the first epitaxial region 27, and the second epitaxial region 54. Thus, the channel region 6 p may be prevented from being degraded by P-type impurities, and the contact resistance between the source/drain region 21 a and the contact structure 57 may be significantly reduced. Therefore, performance of a transistor may be improved.

Hereinafter, various modified examples of a semiconductor device according to an example embodiment of the present disclosure will be described. Hereinafter, the same numerals may refer to the same component. Thus, in the following description of the modified examples, descriptions of components overlapping with the above-described components will be omitted, and description will be given based on components which are modified or which are to be replaced.

Next, referring to FIGS. 3A to 3D, various modified examples of a semiconductor device according to an example embodiment of the present disclosure will be described. FIGS. 3A to 3D are partially enlarged views corresponding to a region, in which a portion indicated by ‘A’ of FIG. 2A is enlarged, to describe various modified examples of a semiconductor device according to an example embodiment of the present disclosure.

In a modified example, referring to FIG. 3A, a source/drain region 21 b which may replace the source/drain region 21 a of FIG. 2B may be provided.

The source/drain region 21 b may include a base epitaxial region 24, a first epitaxial region 27 b on the base epitaxial region 24, and a second epitaxial region 54 b on the first epitaxial region 27 b.

The second epitaxial region 54 b may include an extended portion 54 p′ extended from a portion overlapping the contact structure 57 and the contact spacer 51 in a direction toward the channel region 6 p and overlapping the gate spacer 15 in the vertical direction D3. The second epitaxial region 54 b may contact the base epitaxial region 24. For example, the extended portion 54 p′ of the second epitaxial region 54 b may contact the base epitaxial region 24.

The first epitaxial region 27 b may include a second lower epitaxial region 27L′ and a second upper epitaxial region 27U′, divided in the vertical direction D3 by the extended portion 54 p′ of the second epitaxial region 54 b. The second upper epitaxial region 27U′ may be disposed on the second lower epitaxial region 27L′. An upper end 27 t of the second upper epitaxial region 27U′ may be in contact with a lower surface of the gate spacer 15.

In a modified example, referring to FIG. 3B, a source/drain region 21 c which may replace the source/drain region 21 a of FIG. 2B may be provided.

The source/drain region 21 c may include the base epitaxial region 24, a first epitaxial region 27 on the base epitaxial region 24, and a second epitaxial region 54 c on the first epitaxial region 27.

In another example, in the embodiment of FIG. 3B, the first epitaxial region 27 may be replaced with the first epitaxial region 27 b described with reference to FIG. 3A.

An upper surface 54 cU of the second epitaxial region 54 c may be disposed at a level higher than a lower surface of the gate spacer 15 and an upper surface of the channel region 6 p.

The second epitaxial region 54 c may include the extended portion 54 p of the second epitaxial region 54 of FIG. 2B.

In another example, in the embodiment of FIG. 3B, the extended portion 54 p of the second epitaxial region 54 c may be replaced with the extended portion 54 p′ of the second epitaxial region 54 b described with reference to FIG. 3A.

In a modified example, referring to FIG. 3C, a contact spacer 51′, which may replace the contact spacer 51 of FIG. 2B, and a source/drain region 21 d, which may replace the source/drain region 21 a of FIG. 2B, may be provided.

A lower end 51L′ of the contact spacer 51′ may be disposed at a height level higher than a lower surface of the gate spacer 15. The metal-semiconductor compound layer 60 may contact the gate spacer 15.

The source/drain region 21 d may include a base epitaxial region 24, a first epitaxial region 27 d on the base epitaxial region 24, and a second epitaxial region 54 d on the first epitaxial region 27 d. The metal-semiconductor compound layer 60 may contact the base epitaxial region 24.

The first epitaxial region 27 d may have a recessed surface 27 r.

The first epitaxial region 27 d may have a pointed upper end 27 t′, while the recessed surface 27 r may be recessed from the upper end 27 t′. The first epitaxial region 27 d may be spaced apart from the contact spacer 51′ and the gate spacer 15.

The second epitaxial region 54 d may be extended from a portion overlapping the contact structure 57 in a direction toward the channel region 6 p (for example, the D1 direction of FIG. 1) and may overlap the contact spacer 51′ and the gate spacer 15 in a vertical direction D3. The second epitaxial region 54 d may be in contact with the base epitaxial region 24.

The second epitaxial region 54 d may be spaced apart from the contact spacer 51′ and the gate spacer 15. The upper surface 54 dU of the second epitaxial region 54 d may be disposed at a height level lower than an upper surface of the channel region 6 p and a lower surface of the gate spacer 15.

In a modified example, referring to FIG. 3D, together with the contact spacer 51′ of FIG. 3C, a source/drain region 21 e, which may replace the source/drain region 21 d of FIG. 3C, may be provided.

The source/drain region 21 e may include the base epitaxial region 24, the first epitaxial region 27 d of FIG. 3C on the base epitaxial region 24, and a second epitaxial region 54 e on the first epitaxial region 27 d.

The upper surface 54 eU of the second epitaxial region 54 e may be disposed at a height level higher than an upper surface of the channel region 6 p and a lower surface of the gate spacer 15. The upper surface 54 eU of the second epitaxial region 54 e may be planar and parallel to the upper surface of the semiconductor substrate 3. The second epitaxial region 54 e may be in contact with the contact spacer 51′ and the gate spacer 15.

Next, referring to FIGS. 4A to 4C, various modified examples of a semiconductor device according to an example embodiment of the present disclosure will be described. FIGS. 4A to 4C are cross-sectional views illustrating various modified examples of a cross-sectional structure of FIG. 2C to describe various modified examples of a semiconductor device according to an example embodiment of the present disclosure.

In a modified example, referring to FIG. 4A, a source/drain region 21 f, which may replace the source/drain region 21 a of FIG. 2C, may be provided.

The source/drain region 21 f may include the base epitaxial region 24, a first epitaxial region 27 on the base epitaxial region 24, and a second epitaxial region 54 f on the first epitaxial region 27.

The upper surface 54 fU of the second epitaxial region 54 f may be disposed at a height level higher than a lower end of the contact spacer 51. The upper surface 54 fU of the second epitaxial region 54 f may have a convex shape in the form of being upwardly rounded.

In the second epitaxial region 54 f, a maximum width of a portion located at a height level lower than a lower end of the contact spacer 51 may be greater than a maximum width of a portion located at a height level higher than a lower end of the contact spacer 51.

In a modified example, referring to FIG. 4B, a source/drain region 21 g, which may replace the source/drain region 21 f of FIG. 4A, may be provided.

The source/drain region 21 g may include the base epitaxial region 24, the first epitaxial region 27 on the base epitaxial region 24, and a second epitaxial region 54 g on the first epitaxial region 27.

The upper surface 54 gU of the second epitaxial region 54 g may be disposed at a height level higher than a lower end of the contact spacer 51. The upper surface 54 fU of the second epitaxial region 54 g may have a shape pointed upwards.

In a modified example, referring to FIG. 4C, a source/drain region 21 h, which may replace the source/drain region 21 g of FIG. 4A, may be provided.

The source/drain region 21 h may include the base epitaxial region 24, a first epitaxial region 27 on the base epitaxial region 24, and a second epitaxial region 54 h on the first epitaxial region 27.

The upper surface 54 hU of the second epitaxial region 541 i may be disposed at a height level higher than a lower end of the contact spacer 51. The upper surface 54 fU of the second epitaxial region 54 h may include a flat upper end and a side surface inclined in a direction from the flat upper end toward the contact spacer 51.

Next, referring to FIGS. 5 and 6, various modified examples of a semiconductor device according to an example embodiment of the present disclosure will be described. FIGS. 5 and 6 are cross-sectional views illustrating various modified examples of a cross-sectional structure of FIG. 2A to describe various modified examples of a semiconductor device according to an example embodiment of the present disclosure.

In a modified example, referring to FIG. 5, the contact structure 57 of FIG. 2A may be replaced with a contact structure 57′, and the contact structure 57′ may include a lower region W1 having a first width, an intermediate region W2 on the lower region W1 and having a second width smaller than the first width, and an upper region W3 on the intermediate region W2 and having a third width wider than the second width. The first width of the lower region W1 may be the same width as the third width of the upper region W3.

A contact spacer 51″, which may replace the contact spacer 51′ of FIG. 2A, may be provided. A portion of the contact spacer 51″ in contact with a portion having a minimum width of the intermediate region W2 of the contact structure 57′ may have a maximum width. A portion of the contact spacer 51″ in contact with the lower region W1 and a portion of the contact spacer 51″ in contact with the upper region W3 may have the same width.

In a modified example, referring to FIG. 6, the channel region 6 p of FIG. 2A may be replaced with a plurality of active layers 6 p′ stacked on the active region 6 while being spaced apart from each other in the vertical direction D3. A gate structure 36 a, which may replace the gate structure 36 of FIG. 2A, may be provided.

The gate structure 36 a may extend lengthwise in the second horizontal direction D2 while covering an upper surface, a side surface, and a lower surface of each of the plurality of active layers 6 p′.

The gate structure 36 a may include a gate dielectric layer 39 a, a gate electrode 42 a, and a gate capping layer 45 a.

The gate electrode 42 a may extend lengthwise in the second horizontal direction D2 while covering an upper surface, a side surface, and a lower surface of each of the plurality of active layers 6 p′, while the gate dielectric layer 39 a may be interposed between the gate electrode 42 a and the plurality of active layers 6 p′, between the gate electrode 42 a and the active region 6, and between the gate electrode 42 a and the isolation layer 9, while covering a side surface of the gate electrode 42 a.

In an example, an inner insulating spacer 34, interposed between the source/drain region 21 a, and the gate dielectric layer 39 a, located below each of the plurality of active layers 6 p′, may be further included. The inner insulating spacer 34 may be omitted.

An upper surface of the channel region 6 p described with reference to FIGS. 2A to 2C may be considered as an upper surface of an uppermost active layer of the plurality of active layers 6 p′. Thus, as described with reference to FIGS. 1 and 2A to 2C, when an upper surface of the uppermost active layer is considered as a reference plane, a maximum depth of the recessed surface 27 r of the first epitaxial region 27 may be about 5 nm to about 50 nm.

Next, referring to FIGS. 7 and 8, a modified example of a semiconductor device according to an example embodiment of the present disclosure will be described. FIG. 7 is a plan view illustrating a modified example of a semiconductor device according to an example embodiment of the present disclosure, and FIG. 8 is a cross-sectional view illustrating a region taken along line IIIa1-IIIa1′ of FIG. 7.

In a modified example, referring to FIGS. 7 and 8, a semiconductor device 100 may include a plurality of active regions 106, which may replace the active region (6 of FIGS. 1 to 2C) described with reference to FIGS. 1 to 2C.

In an example, the active regions 106 may be provided as two or more active regions.

Hereinafter, for convenience of description, an example will be mainly described, in which the active region 106 includes a pair of first and second active regions parallel to each other.

The semiconductor device 100 may include a gate structure 136 corresponding to the gate structure 36 as described with reference to FIGS. 1 to 2C.

The gate structure 136 may overlap the first active region and the second active region of the active regions 106, which are parallel to each other.

The gate structure 136 may be the same as the gate structure 36, described with reference to FIGS. 1 to 2C.

The semiconductor device 100 may further include an isolation layer 109 defining the active regions 106 on the semiconductor substrate 103. The semiconductor substrate 103 and the isolation layer 109 may be the same as the semiconductor substrate 3 and the isolation layer 9, respectively, as described with reference to FIGS. 1 to 2C.

The semiconductor device 100 may further include a gate spacer 115 on a side surface of the gate structure 136. The gate spacer 115 may be formed of the same material as the gate spacer 15, described with reference to FIGS. 1 to 2C.

The semiconductor device 100 may further include an interlayer insulating layer 130 on the isolation layer 109, a source/drain region 121 a overlapping the first active region and the second active region of the active regions 106 and next to the gate structure 136, a contact plug 163 on the source/drain region 121 a, and a contact spacer 151 surrounding a side surface of the contact plug 161 The contact plug 163 may be disposed in a contact hole 148 passing through the interlayer insulating layer 130. The interlayer insulating layer 130, the contact hole 148, and the contact spacer 151 may be formed of the same materials as the interlayer insulating layer 30, the contact hole 48, and the contact spacer 51, respectively, as described with reference to FIGS. 1 to 2C.

In the semiconductor device 100, a cross-sectional structure, cut in the first horizontal direction D1 based on the center of each of the active regions 106, may be the same as a cross-sectional structure cut along line Ia-Ia′ of FIG. 1. Thus, in the semiconductor device 100, the cross-sectional structure, cut in the first horizontal direction D1 based on the center of each of the active regions 106, may be easily understood from the cross-sectional structure cut along line Ia-Ia′ of FIG. 1, for example, a cross-sectional structure of FIG. 2A, so a description thereof will be omitted.

The source/drain region 121 a may be formed of materials the same as the source/drain region 21 a of FIGS. 2A to 2C. For example, the source/drain region 121 a may include base epitaxial regions 124 formed on the first active region and the second active region of the active regions 106, which are parallel to and spaced apart from each other, a first epitaxial region 127 in contact with the base epitaxial regions 124, extending in the second horizontal direction D2 from a portion overlapping the first active region to a portion overlapping the second active region, and a second epitaxial region 154 grown epitaxially from a recessed surface 127 r of the first epitaxial region 127. The second epitaxial region 154 may extend in the second horizontal direction D2 from a portion overlapping the first active region to a portion overlapping the second active region. For example, each of the first epitaxial region 127 and the second epitaxial region 154 may overlap both the first active region and the second active region in the vertical direction D3.

An air gap 120 may be formed between the first epitaxial region 127 and the isolation layer 109.

In an example, the lowest surface portion of an upper surface 254U of the second epitaxial region 254 may be located at a height level lower than a lower end of the contact spacer 151.

The contact plug 157 may be formed of materials the same as the contact structure 57 of FIGS. 2A to 2C. For example, the contact plug 157 may include a metal-semiconductor compound layer 160 in contact with the second epitaxial region 154 and a contact plug 163 on the metal-semiconductor compound layer 160. The contact plug 163 may include a first conductive layer 166 and a second conductive layer 169. The first conductive layer 166 may cover a lower surface and a side surface of the second conductive layer 169, contacting the lower and side surfaces of the second conductive layer 169.

Next, referring to FIGS. 9A to 9D, various modified examples of a semiconductor device according to an example embodiment of the present disclosure will be described. FIGS. 9A to 9D are cross-sectional views illustrating various modified examples of a cross-sectional structure of FIG. 8 to describe various modified examples of a semiconductor device, according to an example embodiment of the present disclosure.

In a modified example, referring to FIG. 9A, a source/drain region 121 b, which may replace the source/drain region 121 a of FIG. 8, may be provided.

The source/drain region 121 b may include the base epitaxial regions 124, the first epitaxial region 127 on the base epitaxial region 124, and a second epitaxial region 154 b on the first epitaxial region 127.

The upper surface 154 bU of the second epitaxial region 154 b may be disposed at a height level higher than a lower end of the contact spacer 151. The upper surface 154 bU of the second epitaxial region 154 b may have a convex shape in the form of being upwardly rounded. In the second epitaxial region 154 b, a maximum width of a portion located at a height level lower than a lower end of the contact spacer 151 may be greater than a maximum width of a portion located at a height level higher than a lower end of the contact spacer 151.

In a modified example, referring to FIG. 9B, a source/drain region 121 c, which may replace the source/drain region 121 a of FIG. 8, may be provided.

The source/drain region 121 c may include the base epitaxial regions 124, the first epitaxial region 127 on the base epitaxial region 124, and a second epitaxial region 154 c on the first epitaxial region 127.

The upper surface of the second epitaxial region 154 c may be disposed at a height level higher than a lower end of the contact spacer 151. The upper surface of the second epitaxial region 154 c may include convex portions 154 cU in the upwardly rounded form and a concave portion 154 t which is concave downwardly between the convex portions 154 cU in the round form.

In a modified example, referring to FIG, 9C, a source/drain region 121 d, which may replace the source/drain region 121 a of FIG. 8, may be provided.

The source/drain region 121 d may include the base epitaxial regions 124, the first epitaxial region 127 on the base epitaxial region 124, and a second epitaxial region 154 d on the first epitaxial region 127.

The upper surface of the second epitaxial region 154 d may be disposed at a height to level higher than a lower end of the contact spacer 151. The upper surface of the second epitaxial region 154 d may include portions pointed upwards. Thus, the upper surface of the second epitaxial region 154 d may include inclined surfaces 154 dU, portions 154 dt 1 pointed upwards where two inclined surfaces 154 dU meet each other at upper positions, and a portion 154 dt 2 pointed downwardly where two inclined surfaces 154 dU meet each other at a lower position.

In a modified example, referring to FIG, 9D, a source/drain region 121 e, which may replace the source/drain region 121 a of FIG. 8, may be provided.

The source/drain region 121 e may include the base epitaxial regions 124, the first epitaxial region 127 on the base epitaxial region 124, and a second epitaxial region 154 e on the first epitaxial region 127.

The upper surface of the second epitaxial region 154 e may be disposed at a height level higher than a lower end of the contact spacer 151. The upper surface of the second epitaxial region 154 e may include flat upper ends 154 et 1 spaced apart from each other, inclined surfaces 154 eU inclined downwardly from the flat upper ends 154 e 1, and a portion 154 et 2 pointed downwardly, and formed while inclined surfaces between the fiat upper ends 154 e 1 meet each other.

Next, referring to FIGS. 10 and 11A to 11C, a modified example of a semiconductor device according to an example embodiment of the present disclosure will be described.

FIG. 10 is a plan view illustrating a modified example of a semiconductor device according to example embodiments of the present disclosure. FIG. 11 is a cross-sectional view illustrating a region taken along line Ib-Ib′ and a region taken along line IIb-IIb′ of FIG. 10 to describe a modified example of a semiconductor device according to an example embodiment of the present disclosure, FIG. 11B is a partially enlarged view in which a portion indicated by ‘A’ of FIG. 11A is enlarged, and FIG. 11C is a cross-sectional view illustrating a region taken along line IIIb-IIIb′ of FIG. 10 to describe a semiconductor device according to an example embodiment of the present disclosure.

Referring to FIGS. 10 to 11C, a semiconductor device 200 may include a semiconductor substrate 203, an active region 206 and an isolation layer 209, on the semiconductor substrate 203, and a channel region 206 p and a source/drain region 221 a, on the active region 206.

In an example, the active region 206 may be provided as a single active region (see, e.g., active region 6 of FIG. 1), or a plurality of active regions (see, e.g., active regions 106 of FIG. 7). Hereinafter, the case in Which the active region 206 is provided as a plurality of active regions will mainly be described.

The isolation layer 209 may be a trench isolation layer defining the active regions 206. The semiconductor substrate 203 and the isolation layer 209 may be formed of the same materials as the semiconductor substrate 3 and the isolation layer 9, respectively, as described with reference to FIGS. 1 to 2C.

In an example, the channel region 206 p may be extended from each of the active regions 206 in the vertical direction D3. Thus, the channel region 206 p may be provided as a plurality of channel regions.

When the channel regions 206 p are a channel region of an NMOS transistor, the channel region 6 p may have P-type conductivity, and the source/drain region 221 a may have N-type conductivity.

The semiconductor device 200 may include a gate structure 236, a gate spacer 215, an interlayer insulating layer 230, a contact hole 248, a contact structure 257, and a contact spacer 251 corresponding to, and formed of the same materials as, the gate structure 36, the gate spacer 15, the interlayer insulating layer 30, the contact hole 48, the contact structure 57, and the contact spacer 51, respectively, as described with reference to FIGS. 1 to 2C. For example, the contact structure 257 may include a metal-semiconductor compound layer 260 and a contact plug 263 including the first and second conductive layers 266 and 269, corresponding to the metal-semiconductor compound layer 60 and the contact plug 63 including the first and second conductive layers 66 and 69, respectively, as described with reference to FIGS. 1 to 2C. The metal-semiconductor compound layer 260 may have a thickness in the vertical direction D3 of about 1 nm to about 10 nm.

The semiconductor device 200 may include a source/drain region 221 a which may replace the source/drain region 21 a described with reference to FIGS. 1 to 2C.

An air gap 220 may be disposed between the source/drain region 221 a and isolation layer 209 in the region between the active regions 206.

The source/drain region 221 a may include base epitaxial regions 224 formed on the first active region and the second active region of the active regions 206, which are parallel to each other and spaced apart from each other, a first epitaxial region 227 in contact with the base epitaxial regions 224, extending in the second horizontal direction D2 from a portion overlapping the first active region to a portion overlapping the second active region, and a second epitaxial region 254 grown epitaxially from a recessed surface 227 r of the first epitaxial region 227. The second epitaxial region 254 may extend in the second horizontal direction D2 from a portion overlapping the first active region to a portion overlapping the second active region. For example, each of the first epitaxial region 227 and the second epitaxial region 254 may overlap both the first active region and the second active region in the vertical direction D3.

The air gap 220 may be formed between the first epitaxial region 127 and the isolation layer 109.

The source/drain region 221 a will be mainly described with reference to FIG. 11B.

Referring to FIG. 11B, the source/drain region 221 a may be disposed in a recess region 218 in the active region 206 and the channel region 206 p.

The source/drain region 221 a may include N-type impurities such as phosphorus (P), arsenic (As), or the like. The N-type impurities in the source/drain region 221 a may be a concentration of 1E17 to 1E22 atom/cc.

The source/drain region 221 a may be a Si epitaxial layer. In another example, the source/drain region 221 a may be a Si epitaxial layer including stibium (Sb) or carbon (C).

The base epitaxial region 224 may have a thickness reduced toward an upper surface of the channel region 206 p. Here, thickness may refer to the distance from an outer surface of the base epitaxial region 224 (e.g., a surface in contact with the channel region 206 p) to an inner surface of the base epitaxial region 224 (e.g., a surface in contact with the first epitaxial region 227). The base epitaxial region 224 may have a thickness in the vertical direction D3 of about 1 nm to about 40 nm below a lower surface of the first epitaxial region 227.

In an example, the base epitaxial region 224 may be omitted.

In an example, the first epitaxial region 227 may have a thickness in the vertical direction D3 of about 1 nm to about 50 nm.

In an example, the second epitaxial region 254 may have a thickness in the vertical direction D3 of about 1 nm to about 50 nm.

In an example, an impurity concentration in the second epitaxial region 254 may be higher than an impurity concentration in the first epitaxial region 227.

In an example, an impurity concentration in the first epitaxial region 227 may be higher than an impurity concentration in the base epitaxial region 224.

In an example, when an upper surface of the channel region 206 p or a lower surface of the gate spacer 215 is considered as a reference plane, a maximum depth of a recessed surface 227 r of the first epitaxial region 227 may be about 5 nm to about 50 nm. For example, the maximum depth of the recessed surface 227 r may be about 5 nm to about 50 nm below the reference plane defined by the lower surface of the gate spacer 215 or the upper surface of the channel region 206 p.

The second epitaxial region 254 may include an extended portion 254 p extending in the first horizontal direction D1 from a portion overlapping the contact structure 257 to a portion overlapping the contact spacer 251. For example, the extended portion 254 p of the second epitaxial region 254 may overlap the contact structure 257 and the contact spacer 251 in the vertical direction D3.

The extended portion 254 p of the second epitaxial region 254 may overlap the gate spacer 215 in the vertical direction D3. The extended portion 254 p of the second epitaxial region 254 may be spaced apart from the gate spacer 215. The second epitaxial region 254 may be in contact with a lower end 251L of the contact spacer 251.

The first epitaxial region 227 may include a first lower epitaxial region 227L positioned below the extended portion 254 p of the second epitaxial region 254 and a first upper epitaxial region 227U positioned above the extended portion 254 p of the second epitaxial region 254. For example, the first lower epitaxial region 227L may be the portion of the first epitaxial region 227 that is formed at a vertical level lower than the extended portion 254 p, and the first upper epitaxial region 227U may be the portion of the first epitaxial region 227 that is formed at a vertical level the same as or higher than the extended portion 254 p. The first lower epitaxial region 227L and the first upper epitaxial region 227U may be connected to each other. For example, the first lower epitaxial region 227L and the first upper epitaxial region 227U may be in material continuity with one another. An upper end 227 t of the first epitaxial region 227 may be in contact with a lower surface of the gate spacer 215.

In an example, the lowest surface portion of an upper surface 254U of the second epitaxial region 254 may be located at a height level lower than a lower end of the contact spacer 251. The upper surface 254U of the second epitaxial region 254 may be disposed at a height level lower than an upper surface of the channel region 206 p.

Next, referring to FIGS. 12A to 12D, various modified examples of a semiconductor device according to an example embodiment of the present disclosure will be described. FIGS. 12A to 12D are partially enlarged views corresponding to a region, in which a portion indicated by ‘B’ of FIG. 11A is enlarged, to describe various modified examples of a semiconductor device according to an example embodiment of the present disclosure.

In a modified example, referring to FIG. 12A, a source/drain region 221 b, which may replace the source/drain region 221 a of FIG. 11B, may be provided.

The source/drain region 221 b may include the base epitaxial region 224, a first epitaxial region 227 on the base epitaxial region 224, and a second epitaxial region 254 b on the first epitaxial region 227.

The upper surface 254U of the second epitaxial region 254 b may be disposed at a height level higher than an upper surface of the channel region 206 p.

In a modified example, referring to FIG. 12B, a source/drain region 221 c and a contact spacer 251′, which may replace the source/drain region 221 a and the contact spacer 251 of FIG. 11B, respectively, may be provided.

A lower end 251L′ of the contact spacer 251′ may be placed at a height level higher than a lower surface of the gate spacer 215.

The source/drain region 221 c may include the base epitaxial region 224, a first epitaxial region 227 on the base epitaxial region 224, and a second epitaxial region 254 c on the first epitaxial region 227.

The upper surface 254 cU of the second epitaxial region 254 c may be disposed at a height level lower than an upper surface of the channel region 206 p.

In a modified example, referring to FIG. 12C, together with e contact spacer 251′ of FIG. 12B, a source/drain region 221 d which may replace the source/drain region 221 a of FIG. 11B, may be provided.

The source/drain region 221 d may include the base epitaxial region 224, a first epitaxial region 227 on the base epitaxial region 224, and a second epitaxial region 254 d on the first epitaxial region 227. The upper surface 254 dU of the second epitaxial region 254 d may be disposed at a height level higher than an upper surface of the channel region 206 p.

Next, referring to FIG. 13, various modified examples of a semiconductor device according to an example embodiment of the present disclosure will be described. FIG. 13 is a cross-sectional view illustrating a modified example of a cross-sectional structure of FIG. 11C to describe a modified example of a semiconductor device according to an example embodiment of the present disclosure.

Referring to FIG. 13, a source/drain region 221 e, which may replace the source/drain region 221 a of FIG. 11C, may be provided.

The source/drain region 221 e may include the base epitaxial region 224, a first epitaxial region 227 on the base epitaxial region 224, and a second epitaxial region 254 e on the first epitaxial region 227.

The upper surface 254 eU of the second epitaxial region 254 e may be disposed at a height level higher than a lower end of the contact spacer 251. The upper surface 254 eU of the second epitaxial region 254 e may have a convex shape in the form of being upwardly rounded. In the second epitaxial region 254 e, a maximum width of a portion located at a height level lower than a lower end of the contact spacer 251 may be greater than a maximum width of a portion located at a height level higher than a lower end of the contact spacer 251.

Next, referring to FIG. 14, a modified example of a semiconductor device according to an example embodiment of the present disclosure will be described. FIG. 14 includes cross-sectional views illustrating various modified examples of a cross-sectional structure of FIG. 11A to describe various modified examples of a semiconductor device according to an example embodiment of the present disclosure.

In a modified example, referring to FIG. 14, the channel region 206 p of FIG. 1A may be replaced with a plurality of active layers 206 p′ stacked while being spaced apart from each other in the vertical direction D3 on the active region 206. A gate structure 236 a, which may replace the gate structure 236 of FIG. 11A, may be provided.

The gate structure 236 a may be extended in the second horizontal direction D2 while covering an upper surface, a side surface, and a lower surface of each of the plurality of active layers 206 p′.

The gate structure 236 a may include a gate dielectric layer 239 a, a gate electrode 242 a, and a gate capping layer 245 a, The gate dielectric layer 239 a, the gate electrode 242 a, and the gate capping layer 245 a may correspond to the gate dielectric layer 39 a, the gate electrode 42 a, and the gate capping layer 45 a, respectively, as described with reference to FIG. 6.

In an example, an inner insulating spacer 234, interposed between the source/drain region 221 a, and the gate dielectric layer 239 a, located below each of the plurality of active layers 206 p′, may be further included. The inner insulating spacer 234 may be omitted.

Next, a method of forming a semiconductor device according to example embodiments of the present disclosure will be described. FIG. 15 is a process flow diagram illustrating a method of forming a semiconductor device according to example embodiments of the present disclosure, and FIGS. 16A to 18B are cross-sectional views illustrating a method of forming a semiconductor device according to an example embodiment of the present disclosure. In FIGS. 16 A to 18B, FIGS. 16A, 17A, and 18A are cross-sectional views illustrating a region taken along line Ia-Ia′ and a region taken along line IIa-IIa′, of FIG. 1, and FIGS. 16B, 17B, and 18B are cross-sectional views illustrating a region taken along line IIIa-IIIa′ of FIG. 1 to describe a semiconductor device, according to an example embodiment of the present disclosure.

Referring to FIGS. 15, 16A, and 16B, an isolation layer 9 defining an active region 6 may be formed on the semiconductor substrate 3.

In an example, the active region 6 may have a linear shape or a bar shape extending lengthwise in a first horizontal direction D1.

The first horizontal direction D1 may be parallel to an upper surface of the semiconductor substrate 3.

In an example, the isolation layer 9 may be a trench isolation layer (a shallow trench isolation layer). The isolation layer 9 may be formed of an insulating material such as silicon oxide, or the like.

In an example, the active region 6 may include a channel region 6 p located at a level higher than an upper surface of the isolation layer 9.

The channel region 6 p of the active region 6 may have N-type conductivity or P-type conductivity. For example, when the channel region 6 p is a channel region of an NMOS transistor, the channel region 6 p may have P-type conductivity. Alternatively, when the channel region 6 p has a channel region of a PMOS transistor, the channel region 6 p may have an N-type conductivity.

A sacrificial structure 12 may be formed (S10). The sacrificial structure 12 may overlap the active region 6 and the isolation layer 9 on the semiconductor substrate 3.

The sacrificial structure 12 may have a linear shape or a bar shape extending lengthwise in a second horizontal direction D2 perpendicular to the first horizontal direction D1.

The second horizontal direction D2 may be parallel to an upper surface of the semiconductor substrate 203.

The sacrificial structure 12 may be provided as a plurality of sacrificial structures.

In an example, the sacrificial structure 12 may include polysilicon.

A gate spacer 15 may be formed on a side surface of the sacrificial structure 12.

The gate spacer 15 may be formed of a single material layer or a mixed material layer.

A source/drain recess region 18 may be formed (S20). Forming of a source/drain recess region 18 may include etching the channel region 6 p of the active region 6 using an etching process using the sacrificial structure 12 and the gate spacer 15 as an etch mask. The source/drain recess region 18 may be formed in the channel region 6 p of the active region 6.

In the source/drain recess region 18, a first epitaxial region 27 may be formed (S30).

In another example embodiment, before the first epitaxial region 27 is formed, forming of a base epitaxial region 24 may be further included, and the base epitaxial region 24 may be grown epitaxially from a surface of the source/drain recess region 18 of the channel region 6 p.

The first epitaxial region 27 may be grown epitaxially from a surface of the base epitaxial region 24.

When the channel region 6 p has N-type conductivity, the base epitaxial region 24 and the first epitaxial region 27 may be formed to have P-type conductivity.

In an example, the base epitaxial region 24 and the first epitaxial region 27 may form a preliminary source/drain region 21.

Referring to FIGS. 15, 17A, and 17B, an interlayer insulating layer 30 may be formed (S40). The interlayer insulating layer 30 may cover the preliminary source/drain region 21 and the isolation layer 9 while being adjacent to the sacrificial structure 12. The interlayer insulating layer 30 may he formed of an insulating material such as silicon oxide.

The sacrificial structure 12 of FIGS. 16A and 16B may be replaced with a gate structure 36 (S50).

Replacing the sacrificial structure 12 of FIGS. 16A and 16B with the gate structure 36 may include forming a gate trench 33 by selectively removing the sacrificial structure 12, and forming the gate structure 36 in the gate trench 33.

The forming of the gate structure 36 in the gate trench 33 may include forming of a gate dielectric layer 39 covering an inner wall of the gate trench 33, forming of a gate electrode 42 partially filling the gate trench 33 on the gate dielectric layer 39, and forming a gate capping layer 45 filling a remaining portion of the gate trench 33 on the gate electrode 42.

Referring to FIGS. 15, 18A, and 18B, a contact hole 48 may he formed (S60). The contact hole 48 may expose the preliminary source/drain region 21 while passing through the interlayer insulating layer 30.

A contact spacer 51 may be formed on a side wall of the contact hole 48 (S70).

The first epitaxial region 27 of the preliminary source/drain region 21 is partially etched, to form a recessed surface 27 r of the first epitaxial region 27.

In an example, the recessed surface 27 r may be spaced apart from a lower end of the contact spacer 51.

Referring to FIGS. 1, 2A, 2B, and 2C, together with FIG. 15, a second epitaxial region 54, grown epitaxially from the recessed surface 27 r, may be formed (S90). The second epitaxial region 54, the first epitaxial region 27, and the base epitaxial region 24 may form a source/drain region 21 a.

A contact structure 57 may be formed (S100). The contact structure 57 may fill the contact hole 48. The contact structure 57 may include a metal-semiconductor compound layer 60 in contact with the second epitaxial region 54 of the source/drain region 21 a, and a contact plug 63 on the metal-semiconductor compound layer 60.

Formation of the contact structure 57 may include forming the metal-semiconductor compound layer 60 in contact with the second epitaxial region 54 of the source/drain region 21 a by performing a silicide process, and forming the contact plug 63 filling the contact hole 48 on the metal-semiconductor compound layer 60.

Formation of the contact plug 63 may include forming a first conductive layer 66 covering an inner wall of the contact hole 48, and forming a second conductive layer 69 filling the contact hole 48 on the first conductive layer 66.

As set forth above, according to example embodiments of the present inventive concept, a source/drain region may include a base epitaxial region, a first epitaxial region on the base epitaxial region, and a second epitaxial region on the first epitaxial region. The second epitaxial region may be a stressor which could apply stress to a channel region in order to improve charge mobility. The second epitaxial region may be spaced apart from the channel region, and may be in contact with a contact plug. Since an impurity concentration of the second epitaxial region in the source/drain region is the highest, a channel region may be prevented from being degraded by impurities in a source/drain region, while contact resistance between the source/drain region and the contact plug may be significantly reduced. Therefore, performance of a transistor may be improved.

While example embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope of the present disclosure, as defined by the appended claims. 

What is claimed is:
 1. A semiconductor device, comprising: an isolation layer defining a first active region on a semiconductor substrate; an interlayer insulating layer on the isolation layer; a channel region on the first active region; a source/drain region adjacent to the channel region in a first horizontal direction, on the first active region; a gate structure overlapping the channel region and extending lengthwise in a second to horizontal direction perpendicular to the first horizontal direction, on the channel region; a contact structure on the source/drain region; a gate spacer between the contact structure and the gate structure; and a contact spacer disposed between the contact structure and the gate spacer and disposed between the contact structure and the interlayer insulating layer, wherein a lower end of the contact spacer and a lower end of the gate spacer are disposed at different height levels, wherein the contact structure includes a metal-semiconductor compound layer, and a contact plug on the metal-semiconductor compound layer, wherein the source/drain region includes a first epitaxial region having a recessed surface and a second epitaxial region on the recessed surface of the first epitaxial region, wherein an upper surface of the second epitaxial region is in contact with the metal-semiconductor compound layer, wherein the second epitaxial region includes an extended portion, extending lengthwise in the first horizontal direction from a portion overlapping the contact structure in a vertical direction to a portion overlapping the contact spacer in the vertical direction, and wherein the vertical direction is perpendicular to an upper surface of the semiconductor substrate.
 2. The semiconductor device of claim 1, wherein the source/drain region further includes a base epitaxial region, wherein the source/drain region has P-type conductivity, wherein the first epitaxial region is disposed on the base epitaxial region, wherein the base epitaxial region and the first epitaxial region include a silicon (Si) element and a germanium (Ge) element, and wherein a concentration of a Ge element in the first epitaxial region is higher than a concentration of a Ge element in the base epitaxial region.
 3. The semiconductor device of claim 2, wherein the second epitaxial region includes a Ge element with a concentration higher than a concentration of a Ge element in the first epitaxial region.
 4. The semiconductor device of claim 2, wherein the first epitaxial region further includes an upper end in contact with a lower surface of the gate spacer.
 5. The semiconductor device of claim 2, wherein the extended portion of the second epitaxial region is spaced apart from the base epitaxial region.
 6. The semiconductor device of claim 2, wherein the extended portion of the second epitaxial region is in contact with the base epitaxial region.
 7. The semiconductor device of claim I, wherein the contact spacer has a lower end at a height level lower than a lower end of the gate spacer.
 8. The semiconductor device of claim 1, wherein the first epitaxial region is divided by the extended portion of the second epitaxial region into a first lower epitaxial region and a first upper epitaxial region.
 9. The semiconductor device of claim 1, wherein the extended portion of the second epitaxial region overlaps the gate spacer in the vertical direction.
 10. The semiconductor device of claim 1, wherein a lower surface of the contact structure is disposed at a height level lower than a lower end of the gate spacer.
 11. The semiconductor device of claim 1, wherein a lower surface of the contact structure is disposed at a height level higher than a lower end of the gate spacer.
 12. The semiconductor device of claim 1, wherein an upper surface of the first epitaxial region is disposed at a height level lower than an upper surface of the second epitaxial region.
 13. The semiconductor device of claim 1, wherein the contact structure includes a lower region having a first width, an intermediate region on the lower region and having a second width smaller than the first width, and an upper region on the intermediate region and having a third width wider than the second width.
 14. The semiconductor device of claim 1, wherein the channel region extends from the first active region in the vertical direction, and wherein the gate structure extends lengthwise in the second horizontal direction while covering an upper surface and a side surface of the channel region.
 15. The semiconductor device of claim 1, wherein the channel region includes a plurality of active layers stacked while being spaced apart from each other in the vertical direction on the first active region, and wherein the gate structure extends lengthwise in the second horizontal direction while covering an upper surface, a side surface, and a lower surface of each of the plurality of active layers.
 16. The semiconductor device of claim 1, further comprising: a second active region parallel to the first active region on the semiconductor substrate, wherein the gate structure overlaps the first active region and the second active region, wherein the first epitaxial region extends in the second horizontal direction from a to portion overlapping the first active region to a portion overlapping the second active region, and wherein the second epitaxial region extends in the second horizontal direction from a portion overlapping the first active region to a portion overlapping the second active region.
 17. A semiconductor device, comprising: an active region on a semiconductor substrate; a channel region on the active region; a source/drain region adjacent to the channel region on the active region; a gate structure overlapping the channel region, on the channel region; a contact structure on the source/drain region; a gate spacer between the contact structure and the gate structure; and a contact spacer surrounding a side surface of the contact structure, wherein the source/drain region includes a base epitaxial region, a first epitaxial region on the base epitaxial region, and a second epitaxial region on the first epitaxial region, wherein the source/drain region includes a Si element and a Ge element, wherein a Ge element concentration in the base epitaxial region, a Ge element concentration in the first epitaxial region, and a Ge element concentration in the second epitaxial region are different from each other, and wherein the second epitaxial region includes an extended portion, extending in a horizontal direction from a portion overlapping the contact structure in a vertical direction to a portion overlapping the contact spacer in the vertical direction.
 18. The semiconductor device of claim 17, wherein the contact structure includes a metal-semiconductor compound layer, and a contact plug on the metal-semiconductor compound layer, wherein the metal-semiconductor compound layer is in contact with the second epitaxial region, wherein the Ge element concentration in the first epitaxial region is higher than the Ge element concentration in the base epitaxial region, and wherein the Ge element concentration in the second epitaxial region is higher than the Ge element concentration in the first epitaxial region.
 19. A semiconductor device, comprising: an active region on a semiconductor substrate; a channel region on the active region; a source/drain region adjacent to the channel region on the active region; a gate structure overlapping the channel region, on the channel region; a contact structure on the source/drain region; a gate spacer between the contact structure and the gate structure; and a contact spacer surrounding a side surface of the contact structure, wherein the source/drain region includes a first epitaxial region having a recessed surface and a second epitaxial region on the recessed surface of the first epitaxial region, and wherein the second epitaxial region includes an extended portion, extending in a horizontal direction from a portion overlapping the contact structure in a vertical direction to a portion overlapping the contact spacer in the vertical direction.
 20. The semiconductor device of claim 19, wherein a lower end of the contact spacer and a lower end of the gate spacer are disposed at different height levels, wherein the channel region includes a plurality of active layers stacked while being spaced apart from each other in the vertical direction on the active region, wherein the gate structure covers an upper surface, a side surface, and a lower surface of each of the plurality of active layers, and wherein a maximum depth of the recessed surface of the first epitaxial region is 5 nm to 50 nm, where an upper surface of an uppermost active layer of the plurality of active layers is considered as a reference plane. 